/*
 * Copyright (C) 2004, 2005 Joe Walnes.
 * Copyright (C) 2006, 2007, 2009, 2011, 2012 XStream Committers.
 * All rights reserved.
 *
 * The software in this package is published under the terms of the BSD
 * style license a copy of which has been included with this distribution in
 * the LICENSE.txt file.
 * 
 * Created on 06. May 2004 by Joe Walnes
 */
package com.feilong.lib.xstream.core.util;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Wrapper around java.text.SimpleDateFormat that can
 * be called by multiple threads concurrently.
 * <p>
 * SimpleDateFormat has a high overhead in creating
 * and is not thread safe. To make best use of resources,
 * the ThreadSafeSimpleDateFormat provides a dynamically
 * sizing pool of instances, each of which will only
 * be called by a single thread at a time.
 * </p>
 * <p>
 * The pool has a maximum capacity, to limit overhead.
 * If all instances in the pool are in use and another is
 * required, it shall block until one becomes available.
 * </p>
 *
 * @author Joe Walnes
 * @author J&ouml;rg Schaible
 */
public class ThreadSafeSimpleDateFormat{

    private final String   formatString;

    private final Pool     pool;

    private final TimeZone timeZone;

    public ThreadSafeSimpleDateFormat(String format, TimeZone timeZone, int initialPoolSize, int maxPoolSize, final boolean lenient){
        this(format, timeZone, Locale.ENGLISH, initialPoolSize, maxPoolSize, lenient);
    }

    public ThreadSafeSimpleDateFormat(String format, TimeZone timeZone, final Locale locale, int initialPoolSize, int maxPoolSize,
                    final boolean lenient){
        formatString = format;
        this.timeZone = timeZone;
        pool = new Pool(initialPoolSize, maxPoolSize, () -> {
            SimpleDateFormat dateFormat = new SimpleDateFormat(formatString, locale);
            dateFormat.setLenient(lenient);
            return dateFormat;
        });
    }

    public String format(Date date){
        DateFormat format = fetchFromPool();
        try{
            return format.format(date);
        }finally{
            pool.putInPool(format);
        }
    }

    public Date parse(String date) throws ParseException{
        DateFormat format = fetchFromPool();
        try{
            return format.parse(date);
        }finally{
            pool.putInPool(format);
        }
    }

    private DateFormat fetchFromPool(){
        DateFormat format = (DateFormat) pool.fetchFromPool();
        TimeZone tz = timeZone != null ? timeZone : TimeZone.getDefault();
        if (!tz.equals(format.getTimeZone())){
            format.setTimeZone(tz);
        }
        return format;
    }

    @Override
    public String toString(){
        return formatString;
    }
}
